Some of the examples in the promo videos are pretty far-fetched. I mean, does anyone really give Facebook any information about which dentist he or she goes to? I've never even seen a post from someone talking about going to the dentist, let alone including the dentist's actual name!
One of the side effects of people actually using graphsearch would be that businesses need to have more likes than their competitors, to enhance their FB SEO. Therefore, we'll likely see even more FB ads for nearby businesses trying to get you to like their page.